As California heats up over Proposition 37, the November 2012 ballot initiative that could see the state adopt mandatory labeling for all foods containing genetically modified ingredients, new research adds startling cancer concerns to the discussion.

As California heats up over Proposition 37, the November 2012 ballot initiative that could see the state adopt mandatory labeling for all foods containing genetically modified ingredients, new research adds startling cancer concerns to the discussion.

Published in the recent issue of the journal Food and Chemical Toxicology, the study, entitled “Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize,” was conducted at the University of Caen in France, and points to a connection between GMO crops sprayed with the popular glyphosate-based herbicide, commonly marketed as Monsanto’s Roundup and cancer.

According to the research, rats fed a diet containing NK603—a variety of corn seed designed to be tolerant to Roundup treatment—developed mammary tumors and experienced organ damage to the kidneys and liver. Half of the male rats and 70 percent of the female rats died prematurely on the glyphosate-heavy diets compared with the control group that experienced only 20 and 30 percent premature deaths.

The news comes just days after Monsanto made another significant financial contribution of nearly $3 million to defeat Proposition 37. This brings their total contributions against mandatory labeling of genetically modified foods to $7.1 million. Monsanto, the leading manufacturer of glyphosate-based herbicides and genetically modified seeds including corn, soy, canola and cotton, said the study’s conclusions were “unsubstantial.”

The United States is the only industrialized nation to not have a national policy on the labeling of genetically modified foods, despite existing data on the human and environmental health risks. The California Department of Food and Agriculture estimates that roughly 80-90 percent of soy, corn, canola and cotton grown in the country is genetically modified.